In the interactive television market, early efforts for such interactivity have been centered simply on allowing devices such as PCs, set-tops, and net-tops to receive message types and display enhanced content. The industry lacks standard hardware and software and the products of several companies operate on separate systems
Each of these systems is designed to act as a closed system: each cable headend, satellite broadcast system, etc. uses its own hardware and software within the system; digital set-top systems are designed to accept standardized triggers in the broadcast to retrieve additional information; the standardized triggering system can be an unreliable method of delivering interactivity as the triggers can be removed at any part of the line from broadcast through the MSO to the customer; the closed systems do not allow for full, real-time interactivity, but rather just send new information to the user upon request; and because all of the systems are closed, no system allows them all to be connected and provide real-time interactivity among all participants